Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-11-23
2004-06-01
Nguyen, Huy (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06744970
ABSTRACT:
The invention relates to a method for picture coding and a method for picture decoding. The invention furthermore relates to a method for constructing a sub-picture data unit for an electronic apparatus, and also to an electronic apparatus. Apparatuses appertaining to consumer electronics, in particular, are considered as the electronic apparatus. Furthermore, the invention relates to a data carrier for use in an electronic apparatus.
BACKGROUND OF THE INVENTION
The invention is based on a method for picture coding of the generic type of the independent claim
1
. Various picture coding methods are known from video technology. The picture coding method presented here follows a picture coding method which is used to generate so-called sub-picture data units for DVD apparatuses. DVD playback apparatuses of this type are already commercially available and each contain a sub-picture decoding device (“Sub-Picture Decoder”) which can process the abovementioned sub-picture data units. A description of the picture coding method used is found e.g. in the DVD standard “DVD Specification for read-only disc” Part 3, Video Specification, Version 1.0, August 1996, Chapter 5.4.3 Sub-Picture Unit (SPU). The picture decoding method is also explained therein. A detailed description of the abovementioned sub-picture decoding devices is found in EP-A-0 725 541.
According to the DVD standard, the main application for sub-picture data units is e.g. the generation of subtitles on the screen of a television set. The subtitles are then inserted e.g. at the bottom edge of the picture. The bitmap data for a respective subtitle are then stored in the sub-picture data unit. In order to define the location of a subtitle on the screen and also in order to define a number of display characteristics, in particular colour, contrast, etc., simple graphical control commands are specified in the abovementioned DVD standard. Thus, in principle, sub-picture data units can also be used for other purposes, thus e.g. for operating instructions, operator guidance menus, animation pictures, intermission pictures, etc.
The essential parts of a sub-picture data unit according to the DVD standard consist in a data field for the bitmap data of the text to be displayed or, more generally, of the object to be displayed, and also in a second part in which so-called display control command sequences are stored which define the display location, the display time and also the display characteristics of the stored object. In the data field for the bitmap data, it is also perfectly well possible for a plurality of objects to be stored one after the other, which are each retrieved at different times.
If the intention is to provide a plurality of objects in a sub-picture data unit, then the DVD standard prescribes the instruction of respectively providing a corresponding area in the bitmap data field for each object. The bitmap data are then additionally subjected to run length coding in order to achieve picture compression and save memory space.
SUMMARY OF THE INVENTION
The object of the invention is to specify a picture coding method and a picture decoding method which allow the sub-picture data units on the one hand to be simplified and on the other hand to be modified such that memory space is saved yet the possibilities in respect of configuration are not impaired. The object set is achieved by means of the features of the independent claims
1
and
2
and also by means of the features of the independent claim
7
.
In the case of the invention's method for picture coding, a digital picture is divided into at least two sections. A respective number of picture sections are subsequently coded in a combined manner. In this case, a combined pixel is generated in each case from the corresponding pixels in the sections to be combined, to be precise in such a way that the combined pixel is allocated an unambiguous type which corresponds to the distribution of the pixel values in the N-tuple of the corresponding pixels.
In the case of a further picture coding method according to the invention, two or more successive pictures are coded in a combined manner in a corresponding way.
These methods can advantageously be employed very well whenever essentially only two different pixel values are allowed for the individual pixels in the picture sections or pictures. This is the case whenever e.g. text is intended to be displayed in the picture. The picture can then be divided into the pixel values “On” and “Off”. The N-tuple of the corresponding pixels then appears such that either the “On” value or the “Off” value holds true per element. An unambiguous pixel type is then allocated for the distribution of the “On”/“Off” values. In the simplest case, two picture sections are combined with one another. Consequently, the N-tuple consists of a pair of pixels. This case is defined more precisely in claim
3
. If again just the two pixel values “On” and “Off” are allowed, it is necessary to define four different pixel types in accordance with the four different distributions of the pixel values in the respective pair of pixels.
Which pixel type is associated with which case is then defined more precisely in claim
4
for the four possible cases.
Although advantageous, with regard to the picture compression, it is not absolutely necessary for the picture sections that are to be combined to be combined with one another such that they overlap 100%. It is also perfectly allowable for the picture sections that are to be combined to be combined only in a partially overlapping manner, in which case absent pixels outside the overlap area are allocated the “Off” value. This measure is specified in claim
5
. It has the advantage that, in this manner, the picture sections can be enlarged in the vertical direction in a simple way, without a great deal of memory space additionally having to be made available for this purpose.
The combination of two or more picture sections results in a single combined picture section comprising just as many pixels as an individual picture section. The pixel values or pixel types thus obtained can then also be subjected to run length coding for the purpose of further picture compression.
The invention likewise relates to a method for decoding a coded picture, see claim
7
. This method for decoding is characterized in that a section with combined pixel values is decoded in a plurality of passes, in each pass one of the picture sections being reconstructed and different selection rules being employed in each case, which selection rules determine which value is to be assigned to a pixel in the corresponding pass. This method affords the advantage that the previously combined picture sections can be reconstructed without any losses, to be precise all of them one after the other in a plurality of passes, the same data record being accessed in each pass. As already explained above, the picture coding method allows, if appropriate, the saving of memory space for the picture to be displayed.
Advantageous measures, in particular with regard to the special case where only two picture sections or pictures are combined and the individual pixels in the picture sections can only assume the two possible values “On” and “Off”, are mentioned in the dependent claims
8
and
9
.
The invention furthermore consists in a method for constructing a sub-picture data unit for an electronic apparatus according to claim
10
. The sub-picture data unit essentially comprises a data section having the pixel values for the sub-picture and a command section having display control command sequences. For such a method, it is advantageous if the data section having the pixel values for the sub-picture or the sub-pictures is divided into sections and coded in a combined manner, in the way specified in claims
1
to
6
, and that a respective display control command sequence is then provided for the reproduction of the pixel values of one of the combined picture sections.
In this case, it is also advantageous if, in a display control command sequence for the
Schiller Harald
Winter Marco
Fried Harvey D.
Kolodka Joseph J.
Nguyen Huy
Thomson Licensing S.A.
Tripoli Joseph S.
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